Oxidative dehydrogenation process catalyzed by magnesium ferrite

ABSTRACT

Improved catalysts for dehydrogenation can be prepared by coprecipitating the metal containing catalysts from a solution of metal ions in the presence of a high molecular weight polyhydric material such as potato starch. The result of having the polyhydric material present is that the precipitate has the form of a gelatinous precipitate of improved processability. The catalyst itself is more active in dehydrogenations and physically stronger than comparable catalyst prepared by conventional methods.

i States Patent [191 Christman et al.

OXIDATIVE DEHYDROGENATION PROCESS CATALYZED BY MAGNESHUM FERRHTEInventors: Harold F. Christman, Seabrook;

Paul H. Teel, Pasadena, both of Tex.

Assignee: Petro-Tex Chemical Corporation,

Houston, Tex.

Filed: May 16, i972 Appl. No.: 253,820

Related US. Application Data Division of Ser. No. 11289. Feb. 3,abandoned.

0.8. Cl. 260/680 E, 252/468, 252/471,

252/743, 260/669 R, 260/6833 lint. Cl. C07c 5/ 18 Field of Search260/680 E, 669

References Cited UNITED STATES PATENTS 3/l938 Joshua 252/428 [4 Oct. 22,1974 2,697,066 l2/l954 Sieg 208/l36 3,270,080 8/1966 Christmann......260/680 3,671,606 6/l972 Manning 260/680 3,686,347 8/1972 Dean et al.260/680 3.7l6,545 2/1973 Ripley 260/680 Primary ExaminerPaul M.Coughlan, Jr. Attorney, Agent, or Firm-N. Elton Dry [57] ABSTRACT 9Claims, No Drawings OXIDATIVE DEHYDROGENATION PROCESS CATALYZED BYMAGNESIUM FERRITE CROSS-REFERENCE TO RELATED APPLICATION Thisapplication is a division of application Ser. No. 11,289, filed Feb. 3,1970, now abandoned.

BACKGROUND OF THE INVENTION This invention relates to improveddehydrogenation catalysts, their method of preparation, particularlycatalysts for oxidative dehydrogenations and the method of using suchcatalyst.

The types of dehydrogenation catalysts known are quite varied. Thepresent invention is concerned with those dehydrogenation catalystswhich comprise a metal compound or mixture of metal compounds. Suchcompounds include the metal oxides, metal salts such as the halides,phosphates, sulfates, molybdates, tungstates, and the like. Generally,these catalysts can be characterized as compounds containing a metalhaving a polyoxidation state, i.e., a metal having at least twooxidation states, in addition to the zero state. Suitable metals arefound in Groups IVB, VB, VIB, VIIB, Vlll, 1B, IVA, VA and VIA of thePeriodic Table* of elements. Particularly useful polyoxidation statemetals are Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Nb, Mo, Ru, Rh, Pd, Sn, Sb, W,Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi, and Po. It has been found thatinstant process is particularly suitable for the preparation ofoxidative dehydrogenation catalyst. Some excellent oxidativedehydrogenation catalysts include stannic phosphate, lead molybdate,aluminum tungstate, cobalt tungstate, iron oxide, antimony oxide,bismuth molybdate, chromium oxide, tungsten oxide, vanadium oxide andthe like. Suitable oxidative dehydrogenation catalysts can contain onesuch polyoxidation state metal ora mixture of such metal compounds. Veryoften these catalysts will be employed in various combinations with eachother as for example lead molybdate/aluminum tungstate, leadmolybdate/cobalt tungstate, iron oxide/chromium oxide, ironoxide/vanadium oxide, iron oxide/manganese oxide, etc.

Handbook of Chemistry and Physics, 45th. Ed., 1964-1965, The ChemicalRubber Co., Cleveland, Ohio, p. 8-2.

In addition to the polyoxidative state metal, the dehydrogenationcatalysts of the present invention can also contain one or moremono-oxidation state metals which act as promoters, initiators,stabilizers and the like. The single oxidation state metal or metalcompounds include metals from Group IA, 11A, 111B, IVB, VB, VIIB, 18,11B, IIIA and IVA, preferably the divalent metals in these Groups.Specifically among those that are often found in oxidativedehydrogenation catalytic systems are Mg, Al, Ca, Sc, Zn, Sr, Cd and Ba.Aluminum oxide in the form of natural or synthetic molecular sieves hasbeen found to be an effective oxidative dehydrogenation catalyst asshown in U.S. Pat. Nos. 3,173,855 and 3,247,278. Also found in theoxidative dehydrogenation catalysts are compounds of Be, thelanthanides, La, Hf, Ta, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Py, Ho, Er, Tm,Yb, Lu, Di (used to describe a mixture of rare earths, e.g., a Di O- istypically 45 to 46% 1.8. 1 t0 2% CeO 9 to 10% Pr O 32 to 33% Ndgog, 5 t0smgoa, 3 t0 Gd O Ybzoa and 1 to 2% other rare earths), the actinides,e.g., Th, Pa,) Ge, Ga, Y, Zn, Se, Te, and In.

In addition to the metals the catalysts often contain variousnon-metallic components which also serve as promoters, initiators,stabilizers or the like. Alkali metal compounds are frequently presentin the oxidative dehydrogenation catalyst in limited quantities such asU 0, Na O and K 0. Other additives are sulfur, phosphorus, silicon,boron or mixtures thereof, for example, sulfates, sulfites, sulfides,alkylmercaptans, sulfuric acid, phosphates, phosphoric acid, silica,silicates, boron trifluoride and the like. Such additives are disclosedin U.S. Pat. Nos. 3,247,278; 3,270,080; 3,303,238; 3,324,195; 3,398,100.

Halogen is also often present in oxidative dehydrogenation to improvethe results. The presence of halogen in the dehydrogenation zone isparticularly effective when the compound to be dehydrogenatedissaturated, such as a saturated hydrocarbon. The halogen present in thedehydrogenation zone may be either elemental halogen or any compound ofhalogen which would liberate halogen under the conditions of reaction.Suitable sources are such as hydrogen iodide, hydrogen bromide andhydrogen chloride, ethyl iodide, methyl bromide, methyl chloride,1,2-dibromoethane, ammonium iodide, ammonium bromide, ammonium chloride,sulfuryl chloride, etc. The halogen may be liberated partially orentirely by a solid source as shown in U.S. Pat. No. 3,130,241. Mixtureof halogens and halogen sources can be used. The amount of halogen,calculated as elemental halogen, may be as little as about 00001 or lessmole of halogen per mole of organic compound to be dehydrogenated to ashigh as 0.2 or 0.5. The use of halogens in oxidative dehydrogenations isshown in U.S. Pat. Nos. 3,210,436; 3,207,805 3,207,810; 3,277,207;3,278,626; 3,308,182 3,308,200; 3,316,320; 3,356,750; 3,359,343;3,374,283; 3,382,290; 3,440,298; 3,442,968.

In addition to the catalysts described above the following U.S. patentsfurther described oxidative dehydrogenation catalysts generallycontemplated by the instant invention: U.S. Pat. Nos. 3,420,91 1;,3420,912,

Among the preferred catalysts of this invention are those which containiron, oxygen and at least one other metallic element Me. The catalystscomprise crystalline compositions of iron, oxygen, and at least oneother metallic element Me. The catalysts comprise ferrites. Ordinarily,the ionic radius of the second metallic ingredient( s) Me is smallenough that the oxygen anions are not spread too far apart. That is, theelements must be able to form a crystalline structure with the iron andoxygen.

A preferred type of catalyst of this type is that having a face-centeredcubic form of crystalline structure. Examples of this type of catalystare ferrites of the general formula MeOFe o where Me is a divalent metalcation such as Mg-l+ or Ni++. However, if the cations are large, such assr'i-H 1.35 A), the spinel structure may not occur and other types offerrites having a hexagonal crystal of the type SrO' 6Fe O may beformed. These hexagonal ferrites are within the scope of the definitionof catalysts of this invention.

Suitable catalysts may also be ferrites wherein other metals arepartially substituted for the iron. For example, atoms having a valenceof +3 may be partially substituted for someof the Fe-l-l-latoms. Also,metal atoms having a valence of +4 may replace some of the Fe-i-l-lions.However, the catalysts will still suitably have iron present in anamount described above in relation to the total atoms of the secondmetallic ingredient( s).

The catalysts may have the iron combined in crystalline structure withoxygen and more than one other metallic element, as mentioned above. Forexample, a preferred type of ferriteis that essentially or approximatelyof the formula, MeFe where Me represents a divalent metal ion with anionic radius approximately between 0.5 and 1.1 A., preferably betweenabout 0.6 and 1.0 A. In the case of simple ferrites, Me may be, e.g.,one of the divalent ions of the transition elements as Mg, Ca, Sr, Ba,Cr, Mn, Co, Ni, Zn, or Cd. However, a combination of these ions is alsopossible to form a ferrite such as Ni -,Mg 1-e 0 or Ni Mg Fe O Moreover,the symbol Me may represent a combination of ions which have an averagevalency of two. However, it is essential that the crystalline structurecontain iron and the metallic element other than iron.

Examples of catalysts are such as magnesium ferrite, cobalt ferrite,nickel ferrite, zinc ferrite, barium ferrite, strontium ferrite,manganese ferrite, calcium ferrite, cadmium ferrite, silver ferrite,zirconium ferrite, and rare earth ferrites such as cerium ferrite ormixtures of ferrites, such as ferrites containing iron combined with atleast one element selected from the group consisting of Mg, Zn, Ni, Co,Mn, Cu, Cd, Ca, Ba, Sr, Al, Cr, Ti, V, Mo, W, Na, Li, K, Sn, Pb, Sb, Bi,Ga, Ce, La, Th, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu andmixtures thereof, with a preferred group being Mg, Ca, Sr, Ba, Mn, Cr,Co, Ni, Zn, Cd, and mixtures thereof, and particularly preferred metalsbeing Mg or Mn. Examples of mixed ferrites are magnesium ferrite pluszinc ferrite, magnesium ferrite plus nickel ferrite, magnesium ferriteplus cobalt ferrite, magnesium ferrite plus nickel ferrite plux zincferrite, magnesium ferrite plus manganese ferrite. As explained above,these ferrites may be physical mixtures of the ferrites or may containcrystals wherein the different metallic atoms are contained in the samecrystal; or a combination of physical mixtures and chemicalcombinations. Some examples of a chemical combination would be magnesiumzinc ferrite, magnesium chromium ferrite, zinc chromium ferrite andlanthanum chromium ferrite.

The valency of the metals in the catalysts do not have to be anyparticular values, although certain combinations are. preferred ordisclosed elsewhere. The determination of the valency of the ions issometimes difficult and the results are uncertain. The different ionsmay exist in more than one valency state. However, a preferred catalystis one which has the iron predominately in the Fe-l-l-lstate. Someferrites are described in Ferromagnetism, by Richard M. Bozorth (D. VanNostrand Co., Inc., 1951), which disclosure is hereby incorporated byreference.

Although the ferrite catalysts may be broadly defined as containingcrystalline structures of iron, oxygen and the second metallicingredient( s), certain types of catalysts are preferred. Valuablecatalysts were produced comprising as the main active constituent in thecatalyst surface exposed to the reaction gases, iron, oxygen and atleast one element selected from the group of Mn, or Periodic TableGroups 11A, 118 or V111 such as those selected from the group consistingof magnesium, manganese, calcium, cadmium, .cobalt, zinc, nickel,barium, strontium, and mixtures thereof. Preferred catalysts have ironpresent as the predominant metal in the catalyst exposed in the reactiongases.

A preferred class of catalysts containing two second metallicingredients are those of the basic formula Me Cr Fe O, where a can varywithin the range of about 0.1 to about 3, b can vary from greater than 0to less than 2 and c can vary from greater than 0 to less than 3. Me canbe any of the metallic ingredients, other than chromium, previouslydescribed, particularly Periodic Table Groups 11A, 11B, 111 and V111. Inparticular, the metals from these groups that are desirable are Mg, Ba,La, Ni, Zn and Cd.

The preferred compositions exhibit a certain type of X-ray diffractionpattern. The preferred compositions do not have any sharp X-raydiffraction reflection peaks as would be found, e.g., in a highlycrystalline material having the same chemical composition. Instead, theferrite composition of this invention exhibit reflection peaks which arerelatively broad. The degree of sharpness of the reflection peak may bemeasured by the reflection peak band width at half height (W h/2). Inother words, the width of the reflection peak as measured at one-half ofthe distance to the top of the peak is the band width at half height.The band width at half height is measured in units of 2 theta.Techniques for measuring the band widths are discussed, e.g., in Chapter9 of Klug and Alexander, X-ray Diffraction Procedures, John Wiley andSon, N.Y., 1954. The observed band widths at half height of thepreferred com- 'positions of this invention are at least 0.16 2 thetaand normally will be at least 0.20 2 theta.* For instance, excellentcompositions have been made with band widths at half height of at least0.22 or 0.23 "2 theta. The particular reflection peak used to measuredthe band width at one-half height is the reflection peak having Millerhkl) indices of 220. See, e.g., Chapter of Klug and Alexander, ibid).Applicants do not wish to be limited to any theory of the invention inregard to the relationship between composition activity and band width.

*The powder diffraction patterns may be made, e.g., with Norelcoconstant potential diffraction unit type No. 12215/0, equipped with awide range goniometer type No. 42273/0, cobalt tube type No. 321 19,proportional counter type No. 57250/1; all coupled to the Norelcocircuit panel type No. 1206/53. The cobalt K alpha radiation is suppliedby operating the tube at a constant potential of 30 kilovolts and acurrent of 10 milliamperes. An iron filter is used to remove K betaradiation. The detector voltage is 1,660 volts and the pulse heightanalyzer is set to accept pulses with amplitudes between 10 and 30 voltsonly. Slits used are divergence 1, receiving 0.006 inches and scatter 1.Strip chart recordings for identification are made with a scanning speedof A" per minute, time constant of4 seconds and a full scale at 10counts per second. No correction is made for Ka doublet or instrumentalbroadening of the band widths.

Suitable preferred ferrites according to this invention are zincferrites having X-ray diffraction peaks within the d-spacings 4.83 to4.89, 2,95 to 3.01, 2.51 to 2.57, 2.40 to 2.46, 2.08 to 2.14, 1.69 to1.75, 1.59 to 1.65 and 1.46 to 1.52, with the most intense peak beingbetween 2.51 to 2.57; manganese ferrite having peaks at d spacingswithin or about 4.87 to 4.93, 2.97 to 3.03, 2.50 to 2.58, 2.09 to 2.15,1.70 to 1.76, 1.61 to 1.67, and 1.47 to 1.53 with other peaks) with themost intense peak being between 2.52 to 2.58; magnesium ferrites havingpeaks between 4.80 to 4.86, 2.93 to 2.99, 2.49 to 2.55, 2.06 to 2.12,1.68 to 1.73, 1.58 to 1.63 and 1.45 to 1.50 with the most intense peakbeing between 2.49 and 2.55; and nickel ferrites having peaks within thed spacings of 4.79 to 4.85, 2.92 to 2.98, 2.48 to 2.54, 2.05 to 2.11,1.57 to 1.63 and 1.44 to 1.49, with the most intense peak being within2.48 to 2.54. The preferred manganese ferrites are those having the Mnpredominately present as a valence of plus 2.

Ferrite formation may be accomplished by reacting an active compound ofiron with an active compound of the designated metals. By activecompound is meant a compound which is reactive under the conditions toform the ferrite. Starting compounds of iron or the othermetal may besuch as the nitrates, hydroxides, hydrates, oxalates, carbonates,acetates, formates, halides, oxides,etc. The starting compounds aresuitably oxides or compounds which will decompose to oxides during theformation of the ferrite such as organic and inorganic salts orhydroxides. For example, manganese carbonate may be reacted with ironoxide hydrates to form manganese ferrite.

The catalysts may contain anexcess of iron over the stoichiometricamount to form the ferrite. For example, in a ferrite of the type MeFe Othe stoichiometric amount of iron would be 2 atoms per atom of Me. Theiron (calculated as Fe O may be present in an amount of at least aboutpercent in excess of the stoichiometric amount and preferably may bepresent in an amount of at least 14 percent in excess. Suitable rangesof iron are from about 10 to 200 percent excess. Similarly the catalystsmay contain an excess of the Me over the stoichiometric amount required.

The metal ferrite catalysts prepared according to the present inventioncan have higher ratios of iron to metal than were possible before. Thisallows lower inlet temperatures and lower operating temperatures for thedehydrogenation in which the catalysts are employed. Catalysts preparedby prior art methods to give high ratios of iron to metal exhibit arapid time trend in dehydrogenation use, i.e., selectively loss is veryrapid with time. in use.

Various methods have been employed to prepare dehydrogenation catalyst.Although the catalyst may be comprised of a single compound such as ironoxide, it has more often been the case that cocatalysts possessadvantages over the single components such as a magnesium iron oxide.Also as pointed out above various metal and non-metal promoters,initiators, stabilizers and the like are often desirable. Thesecatalysts have been prepared by precipitation, by dry or wet milling ormixing, by precipitation of one of the ingredients in the presence ofthe other, coprecipitation and impregnation of one or more of the solidingredients with aqueous or non-aqueous solutiont s) of salt(s)'of theadditional ingredient(s).

For example, one method previously used for preparing a leadmolybdate/cobalt tungstate was by mixing a soluble salt of lead and asoluble molybdate salt..The lead molybdate is washed free of electrolyteand slurried with an aqueous solution of a soluble cobalt salt which isprecipitated as the tungstate by mixing with a soluble tungstate salt.The resulting precipitate is washed free of electrolyte, dried andcalcined. Metal ferrite oxidative dehydrogenation catalysts, for examplemagnesium ferrite, have been prepared by contacting magnesium oxidepellets with a solution of ferric nitrate, drying and calcining. Ferricoxide catalyst per se is often prepared by precipitation, i.e., asolution of .a soluble salt of iron, FeCl is precipitated by theaddition of a base, NaOH 'to form Fe(OI-I) a genatinous precipitatewhich is then dehydrated.

The prior methods of dehydrogenation catalyst preparation can broadly bedivided into two categories, l) precipitation includingco-precipitation, 2) physical mixing including dry and wet mixing anddeposition of one ingredient from a solution onto a second ingredient.Commercial catalysts are prepared by both general methods. It has beenobserved, however, that catalysts prepared according to one or the otherbroad categories set out above exhibit more or less intrinsic weaknesswhich it is an object of the present invention to overcome.

Catalysts prepared as in category 1) above have been found to begenerally weak in physical resistance. Care is necessary inhandling suchcatalyst and usually they must be employed in beds since their rate ofattrition precludes their economic use in fluidized or moving bedsystems. These catalysts, however, have the advantage in multi-componentcatalyst systems of having very intimate contact of the components. Thecatalysts prepared by the method of category (2) can have thedisadvantages as set out above, although usually one component or thecarrier is selected for physical strength, but will have as a principalinherent disadvantage, a somewhat non-homogenous character, that is tosay, in multi-component catalyst systems there will not be the samedegree or type of intimate relationship achieved with the precipitationmethods.

SUMMARY OF THE INVENTION The present invention provides a new method ofpreparing dehydrogenation catalysts which have the intimate contactdesirable and possible from the precipitation methods of preparation andyet have physical strength superior to the precipitated catalyst.

In the case of oxidative dehydrogenation catalysts, several otherimprovements are obtained by the present invention including the use ofhigher oxygen to hydrocarbon ratios without substantial loss ofselectivity thus higher yields; lower inlet temperatures; and longercatalyst life than analogous but conventionally prepared catalysts,under similar operating conditions.

Another advantage found with the present catalysts is the increasedcontrol of the reaction. Oxidative dehydrogenation reactions areexothermic thus some means must be employed to control the temperature.Two particular means are heat exchanger for heat removal or a diluent,such as steam, in the feed stream. In either case the instant catalystsprovide greater control, but in the adiabatic process it has been foundthat the quantity of steam diluent can be reduced from that nonnallyrequired thus effecting a substantial utility savings.

Briefly stated, one aspect of the present invention is an improvement inthe method of preparing a catalyst for use in dehydrogenation comprisingcontacting a solution of soluble metal component with a precipitatingagent to precipitate an insoluble metal component wherein theimprovement comprises having present with the soluble metal component ahigh molecular weight soluble polyhydric organic compound. As usedherein and in the claims the term metal component is understood to meana single metal compound or mixture of metal compounds having the same ordifferent anions and/or cations.

The mechanism of the polyhydric material is not fully understood. It ispossible for some polyhydric compounds to form complexes with metals,however, this does not appear to be essential to the present invention.The'high molecular weight of the polyhydric material imparts polymericqualities of viscosity and surface tension to the solution. The termpolyhydric is used to describe a material having at least two andpreferably three ormore hydroxyl groups or groups that produce hydroxylgroups under conditions of the preparation. The term high molecularweight is used to mean a material having a molecular weight of at least3,000 number average) or more. The term soluble is used to indicate thatthe polyhydric material is sufficiently soluble to give the improvedcatalyst. It is also generally expected that the precipitating mediumwill be aqueous, however, it is contemplated that other solvents can beemployed within the scope of this invention.

The molecular weight of the soluble polyhydric organic compoundsis notcritical, but it should be appreciated that lower molecular weights thanabout 3,000 do not provide a satisfactory environment for the formationof the gel. It is preferred that the molecular weight is at least 4,000with the upper limit being set by solubility consideration andalso theviscosity of the precipitating medium. Since the precipitating agentmust contact the metal ions, the viscosity of the precipitating mediumcan not be too great. Generally, soluble polyhydric materials that willallow mixing of the metal ions and precipitating agent will not havemolecular weights of greater than 400,000.

The polyhydric organic compounds contemplated include polyhydricalcohols, including polyesters such as those derived from polybasicacids as adipic, succinic, 'sebacatic, azelaic and phthalic; polyols aspentaerythritoLxylitol and sorbitol; polyethers such as the condensationproducts of ethylene oxide, propylene oxide and mixtures thereof withpolyols such as glycerol, pentaerythritol, xylitol, sorbitol andpolysaccharides; and hydrolyzed polymers such as polyvinyl ace tate topolyvinyl alcohol. The polyesters and polyethers are widely known andcommercially. used in the preparation of polyurethane films and foams.

The term polysaccharide is used to describe a polymer having more thantwo sugar units. Of course, the molecular weight consideration wouldpreclude the inclusion of simple sugars, disaccharides, trisaccharides,etc., but could include some octaand nonosaccharides. A particularlypreferred class of polyhydric compounds is polysaccharides having amolecular weight at least about 3,000. Included are polysaccharidescontaining repeating units of a single monosaccharide homoglycans) ormixtures monosaccharide units (heteroglycans), for example, L-fructose,xylan, D- xylose (mono) and tragacanth, D-xylose and D- galacturonicacid (hetero). Thepolysaccharides can contain substituents such as aminosugar units, pentose sugar units, uronic sugar units, sugar groupscontaining ethers and the like.. The polysaccharides can be linear orbranched, although branched polysaccharides, which constitute apreferred class herein, exhibit better solubility-and are less likely toundergo retrogradation than the linear polysaccharides. The type ofglycosidic linkage does not appear to be critical though generally the l4 and i 6 linkages are usually employed because of their abundance.

Some examples of useful polysaccharides are xylan, amylopectins,amylose, fructans, fucan, floridean starch, glycogens, starches, levans,dextrans, capreolan yeast glucan and gums and mucilages such as carob,tragacanth, locust bean, guaran, cashew, lemon, karaya, ghatti, cholla,arabic and damson. A preferred group of polysaccharides is selected fromthe group consisting of potato starch, corn starch, tapioca starch,arrowroot starch, gum arabic, gum tragacanth and dextran.

The high molecular weight polyhydric organic compound is typicallypresent in the metal ion solution in the range of about 0.1 to 11percent by weight based on the weight of metal in the metal component,or more usually 0.1 to 4 percent by weight based on the weight of metalin the metal component.

Soluble metal salts are known for essentially all metals. In specificregard to the metal components of the present invention the followingsoluble metal compounds are illustrative: titanium trichloride, vanadiumdiiodide, chromium III) nitrate, manganese II) titanate, iron (Ill)nitrate, cobalt (II) acetate, nickel nitrate, copper nitrate, niobiumpotassium fluoride, molybdenum dioxydichloride, ruthenium tetrachloride,rhodium dioxide, palladium chloride, stannous chloride, antimonytrichloride, tungsten dioxydichloride, rhenium trichloride, osmiumtrichloride, iridium tribromide, platinum tetrachloride, gold chloride,mercuric nitrate, thallium acetate, lead fluorosilicate, bismuthdioxide, polonium tetrachloride, magnesium selenate, aluminum bromate,calcium chlorate, scandium chloride, zinc sulfate, strontiumtetrasulfide, cadmium sulfate, barium trisulfide, beryllium bromide,lanthanum heptahydrate chloride, cesium carbonate, germaniumtetrafluoride, europium iodide, gallium nitrate, selenium oxide, indiumtrichloride and the like.

In addition'to compounds of the type listed above, less solublecompounds can be employed in conjunction with other materials andtechniques which will increase their solubility. For example, manyinsoluble compounds, e.g., Fe O and MgO, are soluble in hot concentratedacids. The addition of a cooled solution thereof to an alkaline solutionwill result in the precipitation of the insoluble hydroxide. Suchtechniques and manipulations are well known in the art and theirapplication in the operation of the process of the present invention iscontemplated.

The precipitating agent is any compound which contains an ion which whenreacted with the metal ion portion or portions of the catalyst forms aninsoluble compound. In a large number of cases an alkaline material suchas sodium hydroxide, ammonium hydroxide, potassium hydroxide or the likewill cause an insoluble hydroxide to form, e.g. Fe(OI I) Cr(OH) Ni(OHSome examples of insoluble compounds prepared from soluble compounds arelead molybdate from lead nitrate and sodium molybdate, aluminummolybdate from aluminum nitrate and sodium tungstate, cobalt tungstatefrom cobalt nitrate and sodium tungstate, and so forth.

The catalyst preparations are generally carried out at atmosphericpressure, although either sub or super atmospheric pressures, forexample 0.5 to 50 atmospheres, can be employed if the conditionswarrant. Temperature of the catalyst precipitation are relatively mildbeing at approximately room temperature (about 25 C.). Temperatureslower than room can be employed so long as the reactants aresufficiently soluble, generally temperatures no lower than 20C. will beemployed. I-Iigher temperatures can be employed to im prove thesolubility of the reactants, but generally there is no need to exceedabout 100C. At higher temperatures, i.e. 30 50C. or higher, theviscosity effect obtained from the high molecular weight polyhydriccompound is decreased.

The solutions containing the metal ion and the precipitation agent canbe contacted in any of the ways previously employed for precipitationknown and used in the prior art. The two solutions can be mixed togetherwith mild or vigorous agitation depending on the size of particlesdesired. The metal ion containing solution is conveniently sprayed in toa solution of the precipitating agent in the form of droplets or asteady stream. The droplets produce spheres of catalyst and the steadystream a cylindrical type catalyst. The catalysts prepared according tothis invention have been found to have excellent reactivity in oxidativedehydrogenations and superior strength. The catalysts of this inventionare suitable for both fixed and moving bed operations, such as afluidized bed.

In the preparation of the catalysts the high molecular weight polyhydricorganic compound is added to the solution of metal ions. Generally, ifthe ionic metal solution were prepared by heating, the solution iscooled prior to adding the polyhydric compound, usually to 100C, orless, preferably 50C. or less.

The precipitate which is obtained is a gelatinous material thatis easilyfiltered. Previously the precipitates obtained were extremely difficultto process because of their tendency to clog the filtering means. Therecovered filtrate is washed and dried.

The catalyst thus obtained can be used without further treatment,however, greater activity and selectivity are noted when the catalystsare activated by heating at elevated temperatures, e.g. 400 l,100C. in acontrolled atmosphere, e.g., air, nitrogen, helium, a reducingatmosphere such as hydrogen, carbon monoxide and the like.

Metal ferrites may be obtained by conducting the re action to form theferrites at relatively low temperatures, that is, at temperatures lowerthan some of the very high temperatures used for the formation offerrites prepared for semiconductor application. The very intimaterelationship of the metal ferrite reactants obtained by theco-precipitation of the present invention facilitates the reaction.Generally the temperature of reaction for the formation of metalferrites will be less than 1,300C. and preferably less than l,l50C. Thereaction time at the elevated temperature in the formation of the metalferrite catalyst may run from minutes to 4 hours. Some improvement inthe catalytic activity of metal ferrites may be obtained by reducing thecatalyst. The reduction may be accomplished prior to the initialdehydrogenation, or after the catalyst has been used. The reduction maybe accomplished with any effective reducing gas which is capable ofreducing iron to a lower valence such as hydrogen, carbon monoxide, orhydrocarbons. The temperature of reduction can be from 200 to 900C. orhigher.

The preparation of catalysts is often described as an art. Experiencedresearchers and chemists often have difficulty reproducing a particularcatalyst. This defect is even more often encountered in commercialproduction of catalysts. The gel precipitation method of the presentinvention adds the intangible but extremely valuable asset of giving aneasily handled catalyst preparation method for preparing catalystshaving consistent properties.

The catalysts of this invention can be applied to the dehydrogenation ofa wide variety of organic compounds. Such compounds normally willcontain from 2 to 20 carbon atoms, at least ii i l grouping, having aboiling point below about 350C, and may contain other elements, inaddition to carbon and hydrogen such as oxygen, halogens, nitrogen andsulfur. Preferred are compounds having 2 to 12 carbon atoms, andespecially preferred are compounds of 3 to 6 or 8 carbon atoms.

Among the types of organic compounds which may be dehydrogenated bymeans of the process of this invention are nitriles, amines, alkylhalides, ethers, esters, aldehydes, ketones, alcohols, acids, alkylaromatic compounds, alkyl heterocyclic compounds, cycloalkanes, alkanes,alkenes, and the like. illustration of dehydrogenations includepropionitrile to acrylonitrile; propionaldehyde to acrolein; ethylchloride to vinyl chloride; methyl isobutyrate to methyl methacrylate; 2or 3 chlorobutene-l or 2,3 dichlorobutane to chloroprene; ethyl pyridineto vinyl pyridine; ethylbenzene to styrene; isopropylbenzene toa-methylstyrene; ethylchlorohexane to styrene; cyclohexane to benzene;ethane to ethylene to acetylene; propane to propylene or methylacetylene, allene, or benzene; isobutane to isobutylene; n-butane tobutene and butadiene-l,3; nbutene to butadiene-l,3 and vinyl acetylene;methyl butene to isoprene; cyclopentane to cyclopentene andcyclopentadiene-l ,3; n-octane to ethyl benzene and ortho-xylene;monomethylheptanes to xylenes; ethyl acetate to vinyl acetate;2,4,4-trimethylpentane to xylenes; and the like. This invention may beuseful for the formation of new carbon to carbon bonds by the removal ofhydrogen atoms such as the formation of a carbocyclic compound from twoaliphatic hydrocarbon compounds or the formation of a dicyclic compoundfrom a monocyclic compound having an acyclic group such as theconversion of propene to diallyl. Representative materials which aredehydrogenated by the novelprocess of this invention include ethyltoluene, alkyl chlorobenzenes, ethyl naphthalene, isolbutyronitrile,propyl chloride, isobutyl chloride, ethyl fluoride, ethyl bromide,n-pentyl iodide, ethyl dichloride, 1,3 dichlorobutane, 1,4dichlorobutane, the chlorofluoroethanes, methyl pentane, methylethylketone, diethyl ketone, n-butyl alcohol, methyl propionate, andthe like.

suitable dehydrogenation reactions are the following: acyclic compoundshaving 4 to 5 non-quartemary contiguous carbon atoms to thecorresponding olefins, diolefins or acetylenes having the same number ofcarbon atoms, aliphatic hydrocarbons having 6 to 16 carbon atoms and atleast one quaternary carbon atom to aromatic compounds, such as2,4,4-trimethylpentene-l to a mixture of xylenes; acyclic compoundshaving 6 to 16 carbon atoms and no quaternary carbon atoms to aromaticcompounds such as n-hexens to benzene; cycloparaftins and cycloolefinshaving 5 to 8 carbon atoms to the corresponding olefin, diolefin oraromatic compound, e.g., cyclohexane to cyclohexene or cyclohexadiene orbenzene; aromatic compounds having 8 to 12 carbon atoms including one ortwo alkyl side chains of 2 to 3 carbon atoms to the correspondingaromatic with unsaturated side chain such as ethyl benzene to styrene.

The preferred compounds to be dehydrogenated are hydrocarbons with aparticularly preferred class being acyclic non-quaternary hydrocarbonshaving 4 to 5 contiguous cargon atoms or ethyl benzene and the preferredproducts are n-butene-l or 2, butadiene-1,3, vinyl acetylene,2-methyl-l-butene, 3-methy1-1-butene, 3-methyl-2-butene, isoprene,styrene 'or mixtures thereof. Especially preferred as feed are n-butene1or 2 and the methyl butenes and mixtures thereof such as hydrocarbonmixtures containing these compounds in at least 50 mol percent.

The dehydrogenation reaction may be carried out at atmospheric pressure,superatmospheric pressure or at sub-atmospheric pressure. The totalpressure of the system will normally be about or in excess ofatmospheric pressure, although sub-atmospheric pressure may alsodesirably be used. Generally, the total pressurewill be between about 4p.s.i.a. and about 100 or 125 p.s.i.a. Preferably, the total pressurewill be less than about 75 p.s.i.a. and excellent results are obtainedat about atmospheric pressure. v I

The organic compound to be dehydrogenated is contacted with oxygen inorder for the oxygen to oxidatively dehydrogenate the compound. Oxygenmay be fed to the reactor as pure oxygen, as air, as oxygenenriched air,oxygen mixed with diluents, and so forth. Oxygen may also be added inincrements to the dehydrogenation zone Although determinations regardingthe mechanism of reaction are difficult, the process of an oxidativedehydrogenation process is one wherein the predominant mechanism is bythe reaction of oxygen with the hydrogen released from the hydrocarbon.

, The amount of oxygen employed may vary depending upon the desiredresult such as conversion, selectivity and the number of hydrogen atomsbeing removed. Thus, to dehydrogenate butane to butene requires lessoxygen than if the reaction proceedsto. produce butadiene. Normallyoxygen will be supplied (including all sources, e.g., air to thereactor) in the dehydrogenation zone in an amount from about 0.2 to 1.5,preferably 0.3 to 1.2, mols per mol of H being liberated from theorganic compound, Ordinarily the mols of oxygen supplied will be in therange of from 0.2 to 2.0 mols per mol of organic compound to bedehydrogenated and for most dehydrogenations this will be within therange of 0.25 to 1.5 mols of oxygen per mol or organic compound. Amongthe advantages noted are that the instant catalysts will allow higherratios of oxygen to hydrocarbon than catalyst prepared conventionally.Higher oxygen to hydrocarbon ratios generally provide higher conversionswith a corresponding decrease in selectivity, however, the catalysts ofthe present invention do not exhibit as rapid a decrease in selectivityas the analogous conventionally prepared catalyst thus providing higheryields than were possible previously.

Frequently, the reaction mixture contains a quantity of steam or diluentsuch as nitrogen with the range generally being between about 2 and 40mols of steam per mol of organic compound to be dehydrogenated.Preferably, steam will be present in an amount from about 3 to 3 5 molsper mol of organic compound to be dehydrogenated and excellent resultshave been obtained within the range of about 5 to about 30 mols of steamper mol of organic compound to be dehydrogenated. The functions of thesteam are several-fold, and the steam may not merely act as a diluent.Diluents generally may be used in the same quantities as specified forthe steam. These gases serve also to reduce the partial pressure of theorganic compound.

.The temperature for the dehydrogenation reaction generally will be atleast about 250C, such as greater than about 300C. or 375C, and themaximum temperature in the reactor may be about 700C. or 800C.

or perhaps higher such as 900C. under certain circumstances. However,excellent results are obtained within the range of or about 350 to 700C,such as from or about 400C. to or about 675C. The temperatures aremeasured at the maximum temperature in the dehydrogenation zone.

The gaseous reactants may be conducted through'the reaction chamber at afairly wide range of flow rates. The optimum rlow rates will bedependent upon such variables as the temperature of reaction, pressure,particle size, and so forth. Desirable flow rates may be established byone skilled in the art. Generally the flow rates will be within therange of about 0.10 to 10 liquid volumes of the organic compound to bedehydrogenated per volume of dehydrogenation 'zone containing catalystper hour (referred to as LHSV). Usually, the LHSV will be between 0.15and about 5. For calculation, the volume of a fixed bed dehydrogenationzone containing catalyst is that original void volume of reactor spacecontaining catalyst.

The following examples will further illustrate the invention asdescribed above.

EXAMPLE 1.

This example illustrates the preparation of .a Mg ferrite having aweight ratio of Fe O /MgO of 9/1 by the process of the invention and itsuse in oxidative dehydrogenation. A mixture of Fe O and MgO in theweight ratio of 9 2 1 was digested in hot l50C.) concentrated l-lCl. Thesolution was cooled approximately 40 50 C.) and 2 percent by weight ofpotato starch based on the weight of metal oxides was added withstirring. This solution-sol was sprayed into concentrated aqua ammonia28 percent Nl-l A gelatinous precipitate was produced. The precipitatewas aged for 1 hour, washed with distilled water by decantation,filtered and dried at C. Two. percent by weight of 85% H PO was added tothe dried powder. The mixture was tableted (5/ 32 inch dia.) and driedagain. The tableted catalyst was placed in a reactor tube for testing.The reactor was vertical l-inch diameter lPS stainless steel reactionwith a 10-inch catalyst bed. The re actor was purged with nitrogen andbrought on stream for the conversion of n-butene-Z to butadiene at arate of 1.5 (LHSV),andsteam/hydrocarbon mole ratio of 16 1. Two runswere made at 2 mole ratios of O,jhydrocarbon. The results are shownbelow:

= i= inlet temp. T,,== maximum temp. "'Conversion/Seleclivily/Yield Theunexpected aspect of this catalyst in the oxidative data on magnesiumferrites having even the usual Fez a M Weight ratio of but P p y the 51,580F. in air, and the catalyst of Example 2. The converftlonal methodsllfrrymg 2 and M8 f ditions were the same for both catalyst, i.e., samereactermgi y g 0 3 l y g Wlth Weight tor, bed depth, LHSV,steam/hydrocarbon ratio, ex- E P 85% H3PO4 and redrymg Show butadlenecept for oxygen to hydrocarbon ratio. In order to obieculvlty of 7 9Percent absolute lower for the Same tain comparable temperatures it wasnecessary to use EYE? QRY F E; 10 a higher oxygen to hydrocarbon ratiowith the gel precipitated catalyst. As stated before one of the advan-EXAMPLE 2 4 tages of the catalyst of the present invention is loweroperating temperature, however, for a time trend eval- A mixture of ironchlor1de hexahydride and magnea 1 is were dissolved in water at roomtemperature. To this we f the atal st D fin the g the inlet and mamixture was added 2 percent by weight of dextran havl 0 c y u g X ing amolecular weight of 200,000 300,000 based on mum temp.era.ture.s forboth catalysts a i The f the calcined catalyst calculated as MgFe O Thissoluof the varllanon w g fg gg' l and f tion-sol was sprayed into 28%ammonia solution. A getrend ts are set a latinous precipitate wasobtained. The precipitate was expressed as the defihne m y'eld Per hourson aged, wahed with distilled water, filtered, tableted and Stream TheConventional catalyst on stream y dried at 160C. The catalyst wasemployed as 3/32 inch about hours because l f rapld decllne of calm O.D.pellets. The same apparatus as in Example 1 was y actlvlty- The gelpreclpltated catalyst was on used, the pellets being in a 10-inch fixedbed. The cata- Stf6ff1m for 500 h0llIS- The feed as 6n for 0X- lyst wasactivated by heating. Butene-2 was oxidatively idat ved dehydrogenationto butadiene. dehydrogenated to butadiene in eachrun. The activationconditions of the run and results are shown in EXAMPLE 6 8 The fgqd foreag-h run was These examples demonstrate the preparation and use of anon-oxidative dehydrogenation catalyst according to the invention. Therocedure followed in re arin the catalyst was Table ll.

Example Preparation Fe O /MgO OZIHC Stm/HC T, T,, C i S Y wt. ratio F.C'F.

Gel-Precipitated 9.0; 1 0.55 20 645 920 59 93 2 from chloride salts 0.7520 585 990 74 92 68 1 1 Calcined at tl40F. 0.85 20 59s 1020 79 89 inair. 0.95 20 620 1015 80 88 70 I Gel-Precipitated 9.0 1 0.55 20 635 99059 93 55 3 from chloride salts. 0.75 20 645 1050 70 91 64 Calcined illll40F. 0.85 20 645 1000 78 89 69 in N2.

Gel Precipitated 9.0 1 0.6 15 623 922 60 94 56 4 from chloride salts.0.8 15 624 954 78 9| 7] Calcined at lll0F. 0.9 15 621 1042 79 71 in allTi inlet temp. Tm max temp. C/S/Y conversion/selectivity/yield(mole 'k)O,/HC oxygen/hydrocarbon (mole ratio) Stm/HC Steam/Hydrocarbon (moleratio) TABLE III Time Trend LHSV Og/HC Steam/HC Decline in ButadieneYield CATALYST (hr.) Mole Mole T, F .T,,, "F Mole %/l00 hours vGel-precipitated from 1.5 0.85 20 590/620 1025/1090 0.24 chloride salts,Fe o lMgO wt ratio 9.0:] 3/32"OD pellets, calcined at ll40F In all Mixedoxides 1.5 0.55 20 670/710 1.1

Fe,O;,/Mg0 wt ratio 7.0:1. 3/32" O.D. pellets, calcined at 1580F in air14 A time trend comparison wasmade between a conventionally preparedcatalyst, i.e.., Fe O /MgO weight ratio of 7 :l prepared by slurrying FeO and MgO, forming into 3/32 inch O.D. pellets and calcining at l."Theactive metallic ingredients are digested in hot concentrated acid HCl atapproximately 100-150C).

2. After complete digestion the gelling agent is added to the hot acidmetal solution and thoroughly mixed. in the instant examples 2 percentby weight of gelling agent was added to the active ingredients as awater-gel solution.'The gelling agent'employed in this instance wasDextran 200* which has a molecular weight of 200,000 300,000.

dextran available from Gallard'Schlesinger Chem. Mfg. Corp.

3. The metal-acid-gel mixture was then added in a controlled dropfashion to the precipitating agent, ammonium hydroxide and a gelprecipitate formed.

4. The gel precipitate was washed and filtered with distilled water toremove ammonia and chlorine.

5. After washing, the gel was dried in a forced air oven,screened to a45 mesh size, and calcined in an open air furnace at 850-900C.

6. The catalyst was then slurried with water, pelleted and dried.

The catalyst were evaluated for the dehydrogenation of ethyl benzene tostyrene. For comparison Shell 205 commercial dehydrogenation catalystwas used. The Shell 205 catalyst is believed to be about 85% Fe O and15% K 0 (by wt.). Particular processing, special additives, etc., arenot known. In any event the catalysts were all tested in the same mannerin a pulse microcatalytic reactor. v

The apparatus consisted of a conventional gas chromatograph with a smalltubular stainless steel fixed bed reactor placed in the carrier gasstream between the sampling valve and the partitioning column. Pulses ofreactants were injected at the sample port and mixed with carrier gas(helium) which flowed downward through the one-inch bed of catalyst. Thereaction products were immediately separated on a P and E column, Type R(V con polypropylene operated at 90C and psi.) and quantatively analyzedvia a thermal detector. The carrier gas velocity was constant at 4.6cc/minute which provided a contact time of approximately 0.2 seconds.The conditions and results of the various dehydrogenations are shown inTable IV.

alyst. This solution was sprayed into 28 percent ammonia solution. Agelatinous precipitate was obtained, which was aged for 30 minutes,washed with distilled water, filtered, slurried with solution of H PO,(approximately 1%), coated onto 7-10 mesh AMC (alumina supports,Carbondum Company) and dried at 140C.

The dried pellets were loaded into a 1 inch Vycor reactor in a 13 cc bedand reduced for 1 hour at 450C. After reduction the temperature waslowered to 325C and steam, air and butene-2 feed started. Mole ratio ofsteamzoxygemhydrocarbon 22/0.5/l, LHSV was 1.0. Initial temperatureswere 550-600maximum temperature was 780F. C/S/Y after 4 hours on streamwas 56/94/526. Air was raised to 0.75 and no significant increase intemperature was noted, i.e., maximum 790C. After 4 hours 20 minutes onstream C/S/ Y was 76.6/9l/69.7.

The invention claimed is:

1. In a process for the vapor phase oxidative dehydrogenation of acyclicnon-quarternary hydrocarbons having 4 to 5 contiguous carbon atoms andhaving at least one grouping or ethyl benzene to produce a correspondinghydrocarbon having a higher degree of unsaturation with a magnesiumferrite catalyst wherein the improvement comprises using as themagnesium ferrite catalyst a magnesium ferrite prepared by preparing asolution of soluble metal components of iron and magnesium, adding 0.1to 4 weight percent of a soluble polyhydric organic compound based onthe weight of metal to said solution said polyhydric compound havingnumber average molecular weight of about 3,000 to 400,000 and furtherbeing selected from the group consisting of polyesters derived frompolybasic carboxylic acids and polyols; polyethers being thecondensation products of ethylene oxide, propylene oxide and mixturesthereof with polyols; polysaccharides and mixtures thereof, tingsa so olsolyhls me mpon ts EXAMPLE 9 A mixture of iron chloride hexahydrate andmanganese chloride hexahydrate in a weight ratio of 2:1 was dissolved inwater at room temperature dextran (MW 200,000 300,000 was added to give5 wt. based on the weight MnFe O (calculated) in the finished catandpolyhydric organic compound with a precipitating agent at a temperaturein the range of 20 to C. and at a pressure of 0.5 to 50 atmospheres toprecipitate insoluble metal component of iron and magnesium, recoveringa gelatinous material, and heating said gelatinous material to formmagnesium ferrite.

2. The process according to claim 1 wherein said polyhydric compound isa polyester or polyether.

3. The process according to claim 1 wherein said polyhydric compound isa polysaccharide.

' 4. The process according to claim 3 wherein said polysaccharide isbranched.

5. The process according to claim 4 wherein the polysaccharide has a 14, l 6 or mixed glycoside linkage.

6. The process according to claim 4 wherein said p01- ysaccharide isselected from the group consisting of potato starch, corn starch,tapioca starch, arrowroot starch, gum arabic, gum tragacanth anddextran.

7. The process according to claim 1 wherein the indrocarbons aren-butenes.

1. IN A PROCESS FOR THE VAPOR PHASE OXIDATIVE DEHYDROGENATION OF ACYCLICNON-QUARTERNARY HYDROCARBONS HAVING 4 TO 5 CONTIGUOUS CARBON ATOMS ANDHAVING AT LEAST ONE
 2. The process according to claim 1 wherein saidpolyhydric compound is a polyester or polyether.
 3. The processaccording to claim 1 wherein said polyhydric compound is apolysaccharide.
 4. The process according to claim 3 wherein saidpolysaccharide is branched.
 5. The process according to claim 4 whereinthe polysaccharide has a 1 - 4, 1 - 6 or mixed glycoside linkage.
 6. Theprocess according to claim 4 wherein said polysaccharide is selectedfrom the group consisting of potato starch, corn starch, tapioca starch,arrowroot starch, gum arabic, gum tragacanth and dextran.
 7. The processaccording to claim 1 wherein the insoluble metal component metalcomponent is an oxide, mixture of oxides or compounds that are theprecursors of oxides.
 8. The process according to claim 3 wherein thesoluble metal component is iron oxide and magnesium oxide inhydrochloric acid, the precipitating agent is an alkaline solution andthe insoluble component is iron hydroxide and magnesium hydroxide. 9.The process according to claim 3 wherein the hydrocarbons are n-butenes.